Doubling the duct diameter of a round duct increases its capacity by how many times?

When the diameter of a round duct is doubled, the cross-sectional area of the duct, which determines its capacity, increases significantly. The area of a circle is calculated using the formula A = π(d/2)², where d is the diameter. When the diameter is doubled, the new diameter becomes 2d.

To find the new area, we use the formula:

New area = π((2d)/2)²

= π(d)²

= 4(π(d/2)²)

This means the new area is four times greater than the original area. Since capacity relates directly to cross-sectional area in the case of airflow, doubling the duct diameter increases its capacity by four times.

Consequently, the correct answer is that increasing the duct diameter results in a capacity increase of four times, making it clear that option B (4 Times) is the answer.